Bioremediation is any process that uses microorganisms, fungi, green plants or their enzymes, for treating contamination of the natural environment, caused by wastewater. More particularly, bioremediation uses living systems especially microorganisms to catalyze the degradation of recalcitrant chemicals without disruption of the environment. The main chemical constituents in wastewater released from industrial sectors such as textiles, paper and pulp, oil refineries, pharmaceuticals and food processing units, include but are not limited to dyes, azo dye, reactive dye or a combination therein, aromatic compounds, phenolics, nitrobenzenes. Further, the wastewater also includes organic debris such as cellulosic and hemicellulosic material from fibers, bleaching reagents and other organic solvents. These contribute to colour, chemical oxygen demand (COD), odour, total dissolved solids and other polluting parameters in the discharged water.
Bioremediation can be achieved ex situ or in situ on the basis of removal and transportation of wastes for treatment. In situ bioremediation includes technologies such as bioventing, enhanced biodegradation and phyto-remediation. Some of the advantages of in situ bioremediation methods include minimal site disruption, simultaneous treatment of contaminated soil or water, minimal exposure of public and site personnel, and low costs.
Bioremediation techniques in situ include introduction of different strains of live micro organisms to wastewater at various stages of treatment of the same. Preferably, methods known to exist in the prior art have targeted the sludge formed. The sludge is treated once at the preliminary stage of formation and subsequently after secondary treatment of the wastewater, when activated sludge is obtained. Most of the methods known introduce microbes/bacterial strains in the log phase of growth of the culture. These actively growing microbes consume waste and oxygen for their multiplication and need to be activated at regular intervals leading to increase in the time required for degradation.
Hence, there is a need for reducing the time for degradation and one such method for reducing the time required for degradation is disclosed in US application No 2006/0086659 by Kemira. The method includes the steps of providing an enzyme mixture capable of digesting natural polymeric materials, adding the enzyme mixture to an aqueous sludge suspension, and thereafter, adding at least one species of fermenting bacteria to the suspension, thereby fermenting the resulting suspension.
The addition of enzymes enables digestion of polymeric materials and the microbes added facilitate in fermenting the sludge suspension thereby reducing the time taken for treatment. However, the application is mainly for a sludge suspension and deals with degradation of only natural polymeric materials. Generally, rapid treatment of wastewater is desired even before the stage of formation of sludge. Hence, there is a need for a method that is capable of treating the wastewater rapidly and at any stage of treatment. Also, there is a need for a method for treatment of wastewater that is universally applicable for various kinds of pollutants present in wastewater.
U.S. Pat. No. 4,478,683 describes a method of killing and inhibiting the growth of microorganisms in industrial process streams. The method comprises the addition of an enzymatically catalyzed biocide system utilizing a microbial or plant dehydrogenase enzyme such as peroxidase or laccase in the presence of an oxidant such as hydrogen peroxide or oxygen to oxidize phenolic compounds found in or added to the process streams to produce oxidation products that are toxic to microorganisms.
U.S. Pat. No. 7,285,217 claims a synergistic composition for controlling odour from waste products. The composition comprises a combination of nitrate salt, sulfide-consuming compound, pH-elevating compound, sulfide-oxidizing, nitrate-reducing bacteria, and sulfide-oxidizing enzyme. The method includes adding a sufficient amount of the composition to a waste stream to provide sufficient sulfide-consuming compound to effect immediate removal of sulfide. The composition incorporates a pH elevating compound, which both decreases the amount of gaseous H2S and puts the aqueous phase into a pH range where naturally occurring bacteria can more easily metabolize the sulfide. The composition also includes one or more nitrate salts which will accomplish longer term prevention of odours; Specific bacteria are incorporated into the formulation to insure that the nitrate has the right type and amount of bacteria present to prevent formation of and/or consume sulfide. Specific enzymes are incorporated into the formulation to promote oxidation of sulfide.